The Pythagoreans, Socrates, and Plato attempted to reconcile an element of human freedom with material determinism and causal law. But the first major philosopher to argue convincingly for some indeterminism was probably Aristotle. This is despite the fact that he described a causal chain back to a prime mover or first cause, and he elaborated the four possible causes (material, efficient, formal, and final).

In his Physics and Metaphysics Aristotle also said there were "accidents" caused by "chance (τυχή)." In his Physics, he clearly reckoned chance among the causes. Aristotle might have added chance as a fifth cause - an uncaused or self-caused cause - that happens when two causal chains come together by accident (συμβεβεκός). He noted that the early physicists found no place for chance among the causes.

Aristotle knew that many decisions were quite predictable based on habit and character, but they were no less free if one's character itself and predictable habits were developed freely in the past and were changeable in the future. This was the view of Eastern philosophies and religions. Our karma has been determined by our past actions (even from past lives), and strongly influences our current actions, but we are free to improve our karma by future good actions.

As a principal architect of the concept of causality, and the formulator of the four causes, Aristotle's statements on indefinite causes are perhaps his most significant contribution to freedom, in the world and in human decisions.

Nor is there any definite cause for an accident, but only chance (τυχόν), namely an indefinite (ἀόριστον) cause.

(Metaphysics, Book V, 1025a25)

Without such indefinite (uncaused) causes, everything would happen by necessity.

It is obvious that there are principles and causes which are generable and destructible apart from the actual processes of generation and destruction; for if this is not true, everything will be of necessity: that is, if there must necessarily be some cause, other than accidental, of that which is generated and destroyed. Will this be, or not? Yes, if this happens; otherwise not.

(Metaphysics, Book VI, 1027a29)

Some determinist philosophers have interpreted Aristotle's "accident" as the convergence of two causal chains as being compatible with determinism, but Aristotle himself is unequivocal in opposing strict necessity. Accidents are a consequence of chance.

Aristotle rejected determinism in his statement on chance. Unfortunately, his description of chance as "obscure" (ἄδηλος) to human reason led centuries of philosophers to deny the existence of chance:

Causes from which chance results might happen are indeterminate; hence chance is obscure to human calculation and is a cause by accident.

If then whereas we wish for our end, the means to our end are matters of deliberation and choice, it follows that actions dealing with these means are done by choice, and are voluntary. But the activities in which the virtues are exercised deal with means. Therefore vίrtue also depends on ourselves. And so also does vice. For where we are free to act we are also free to refrain from acting, and where we are able to say No we are also able to say Yes; if therefore we are responsible for doing a thing when to do it is right, we are also responsible for not doing it when not tο dο it is wrong, and if we are responsible fοr rightly not doing a thing, we are also responsible fοr wrongly doing it. But if it is in our power tο dο and tο refrain from doing right and wrong, and if, as we saw, being good οr bad is doing right οr wrong, it consequently depends οn us whether we are virtuous οr vicious.

But if it is manifest that a man is the author of his own actions, if we are unable to trace conduct back to any other origins than those within ourselves, then actions of which the origins are within us (ἐν ἡμῖν), themselves depend upon us (ἐφ' ἡμῖν), and are voluntary (ἐκούσια - willed).

Aristotle challenged those who said our actions are determined by our character. That would deny moral responsibility. He admitted that some aspects of our character may be innate and thus limit our responsibility. But we are at least partially free to form our character.

Even when our character adequately determines our choices, since we were directly responsible for forming at least part of that character at an earlier time in our lives, so we are now indirectly responsible for all those choices.

But suppose somebody says: "All men seek what seems tο them good, but they are not responsible for its seeming gοod: each man's conception οf his end is determined by his character."

If then, as is said, our virtues are voluntary (and in fact we are in a sense ourselves partly the cause of our states of character, and it is our having a certain character that makes us set up an end of a certain kind), it follows that our vices are voluntary also; they are voluntary in the same manner as our virtues.

That Aristotle believes in an open and ambiguous future with alternative possibilities is also shown by his denial of the logical Master Argument for determinism of Diodorus Cronus, in the form of Aristotle's famous "sea battle."

Diodorus argued from an assumed necessity of past truths (which is understandable, if a misapplication of logic to physical reality) that something is impossible that neither is or ever will be true.

Aristotle reframed the argument as the truth or falsity of the statement that a sea battle will occur tomorrow. Despite the law of the excluded middle (or principle of bivalence), which allows no third case (or tertium quid), Aristotle concluded that the statement is neither true nor false, supporting an ambiguous future.

What is, necessarily is, when it is; and what is not, necessarily is not, when it is not. But not everything that is, necessarily is; and not everything that is not, necessarily is not. For to say that everything that is, is of necessity, when it is, is not the same as saying unconditionally that it is of necessity. Similarly with what is not. And the same account holds for contradictories: everything necessarily is or is not, and will be or will not be; but one cannot divide and say that one or the other is necessary.

I mean, for example: it is necessary for there to be or not to be a sea-battle tomorrow; but it is not necessary for a sea-battle to take place tomorrow, nor for one not to take place — though it is necessary for one to take place or not to take place. So, since statements are true according to how the actual things are, it is clear that wherever these are such as to allow of contraries as chance has it, the same necessarily holds for the contradictories also. This happens with things that are not always so or are not always not so. With these it is necessary for one or the other of the contradictories to be true or false — not, however, this one or that one, but as chance has it; or for one to be true rather than the other, yet not already true or false.

Aristotle never denied the law of the excluded middle, merely that the truth or falsity of statements about future events does not exist yet. Note that this implies at least some things in the past may be changed in the future, i.e., the truth values of statements about the future.

In the century following Aristotle, Epicurus proposed a random swerving of some atoms, at no particular places and times, as the cosmological source of chance. Although this physical model for chance is ingenious and anticipated twentieth-century quantum mechanics, Epicurus provides little of deep significance for free will and moral responsibility that is not already implicit in Aristotle.

On the Soul (De Anima)

In Book III, Parts IV and V, perhaps the most controversial and confusing part of his entire corpus, Aristotle says that the soul (psyche) or mind is immaterial. Intellect (nous) is that part of the soul whose active thinking gives it a causal (aitia) power (dynamis) over the material (hyle) body (soma). This claim appears to anticipate the mind-body problem of Descartes, how exactly does an immaterial thing (substance) or property exert a causal force on the material body?

Turning now to the part of the soul with which the soul knows and (whether this is separable from the others in definition only, or spatially as well) we have to inquire what differentiates this part, and how thinking can take place.

If thinking is like perceiving, it must be either a process in which the soul is actted upon by what is capable of being thought, or a process different from but analogous to that. The thinking part of the soul must therefore be, while impassible, capable of receiving the form of an object; that is, must be potentially identical in character with its object without being the object. Thought must be related to what
is thinkable, as sense is to what is sensible...

Thus that in the soul which is called thought (by thought I mean that whereby soul thinks and judges) is, before it thinks, not actually any real thing. For this reason it cannot reasonably be regarded as blended with the body: if so, it would acquire some quality, e.g. warmth or cold, or even have an organ like the sensitive faculty: as it is, it has none. It was a good idea to call the soul 'the place of forms', though this description holds only of the thinking soul, and even this is the forms only potentially, not actually.

De Anima, 429a, J.A.Smith translation, in Jonathan Barnes, The Complete Works of Aristotle, vol. 1, p.682

Part V

Since in every class of things, as in nature as a whole, we find two factors involved, (1) a matter which is potentially all the particulars included in the class, (2) a cause which is productive in the sense that it makes them all (the latter standing to the former, as e.g. an art to its material), these distinct elements must likewise be found within the soul.

And in fact mind as we have described it is what it is what it is by virtue of becoming all things, while there is another which is what it is by virtue of making all things: this is a sort of positive state like light; for in a sense light makes potential colours into actual colours.

Mind in this sense of it is separable, impassible, unmixed, since it is in its essential nature activity (for always the active is superior to the passive factor, the originating force to the matter which it forms).

Actual knowledge is identical with its object: in the individual, potential knowledge is in time prior to actual knowledge, but in the universe as a whole it is not prior even in time. Mind is not at one time knowing and at another not. When mind is set free from its present conditions it appears as just what it is and nothing more: this alone is immortal and eternal (we do not, however, remember its former activity because, while mind in this sense is impassible, mind as passive is destructible), and without it nothing thinks.

But chance also and spontaneity are reckoned among causes: many
things are said both to be and to come to be as a result of chance and
spontaneity. We must inquire therefore in what manner chance and spontaneity
are present among the causes enumerated, and whether they are the same
or different, and generally what chance and spontaneity
are.

Some people even question whether they are real or not. They say
that nothing happens by chance, but that everything which we ascribe to
chance or spontaneity has some definite cause, e.g. coming 'by chance'
into the market and finding there a man whom one wanted but did not expect
to meet is due to one's wish to go and buy in the market. Similarly in
other cases of chance it is always possible, they maintain, to find something
which is the cause; but not chance, for if chance were real, it would seem
strange indeed, and the question might be raised, why on earth none of
the wise men of old in speaking of the causes of generation and decay took
account of chance; whence it would seem that they too did not believe that
anything is by chance. But there is a further circumstance that is surprising.
Many things both come to be and are by chance and spontaneity, and although
know that each of them can be ascribed to some cause (as the old argument
said which denied chance), nevertheless they speak of some of these things
as happening by chance and others not. For this reason also they ought
to have at least referred to the matter in some way or
other.

Certainly the early physicists found no place for chance among
the causes which they recognized-love, strife, mind, fire, or the like.
This is strange, whether they supposed that there is no such thing as chance
or whether they thought there is but omitted to mention it-and that too
when they sometimes used it, as Empedocles does when he says that the air
is not always separated into the highest region, but 'as it may chance'.
At any rate he says in his cosmogony that 'it happened to run that way
at that time, but it often ran otherwise.' He tells us also that most of
the parts of animals came to be by chance.

There are some too who ascribe this heavenly sphere and all the
worlds to spontaneity. They say that the vortex arose spontaneously, i.e.
the motion that separated and arranged in its present order all that exists.
This statement might well cause surprise. For they are asserting that chance
is not responsible for the existence or generation of animals and plants,
nature or mind or something of the kind being the cause of them (for it
is not any chance thing that comes from a given seed but an olive from
one kind and a man from another); and yet at the same time they assert
that the heavenly sphere and the divinest of visible things arose spontaneously,
having no such cause as is assigned to animals and plants. Yet if this
is so, it is a fact which deserves to be dwelt upon, and something might
well have been said about it. For besides the other absurdities of the
statement, it is the more absurd that people should make it when they see
nothing coming to be spontaneously in the heavens, but much happening by
chance among the things which as they say are not due to chance; whereas
we should have expected exactly the opposite.

Others there are who, indeed, believe that chance is a cause, but
that it is inscrutable to human intelligence, as being a divine thing and
full of mystery.

Thus we must inquire what chance and spontaneity are, whether they
are the same or different, and how they fit into our division of
causes.

Part 5

First then we observe that some things always come to pass in the
same way, and others for the most part. It is clearly of neither of these
that chance is said to be the cause, nor can the 'effect of chance' be
identified with any of the things that come to pass by necessity and always,
or for the most part. But as there is a third class of events besides these
two-events which all say are 'by chance'-it is plain that there is such
a thing as chance and spontaneity; for we know that things of this kind
are due to chance and that things due to chance are of this
kind.

But, secondly, some events are for the sake of something, others
not. Again, some of the former class are in accordance with deliberate
intention, others not, but both are in the class of things which are for
the sake of something. Hence it is clear that even among the things which
are outside the necessary and the normal, there are some in connexion withwhich
the phrase 'for the sake of something' is applicable. (Events that are
for the sake of something include whatever may be done as a result of thought
or of nature.) Things of this kind, then, when they come to pass incidental
are said to be 'by chance'. For just as a thing is something either in
virtue of itself or incidentally, so may it be a cause. For instance, the
housebuilding faculty is in virtue of itself the cause of a house, whereas
the pale or the musical is the incidental cause. That which is per se cause
of the effect is determinate, but the incidental cause is indeterminable,
for the possible attributes of an individual are innumerable. To resume
then; when a thing of this kind comes to pass among events which are for
the sake of something, it is said to be spontaneous or by chance. (The
distinction between the two must be made later-for the present it is sufficient
if it is plain that both are in the sphere of things done for the sake
of something.)

Example: A man is engaged in collecting subscriptions for a feast.
He would have gone to such and such a place for the purpose of getting
the money, if he had known. He actually went there for another purpose
and it was only incidentally that he got his money by going there; and
this was not due to the fact that he went there as a rule or necessarily,
nor is the end effected (getting the money) a cause present in himself-it
belongs to the class of things that are intentional and the result of intelligent
deliberation. It is when these conditions are satisfied that the man is
said to have gone 'by chance'. If he had gone of deliberate purpose and
for the sake of this-if he always or normally went there when he was collecting
payments-he would not be said to have gone 'by chance'.

It is clear then that chance is an incidental cause in the sphere
of those actions for the sake of something which involve purpose. Intelligent
reflection, then, and chance are in the same sphere, for purpose implies
intelligent reflection.

It is necessary, no doubt, that the causes of what comes to pass
by chance be indefinite; and that is why chance is supposed to belong to
the class of the indefinite and to be inscrutable to man, and why it might
be thought that, in a way, nothing occurs by chance. For all these statements
are correct, because they are well grounded. Things do, in a way, occur
by chance, for they occur incidentally and chance is an incidental cause.
But strictly it is not the cause-without qualification-of anything; for
instance, a housebuilder is the cause of a house; incidentally, a fluteplayer
may be so.

And the causes of the man's coming and getting the money (when
he did not come for the sake of that) are innumerable. He may have wished
to see somebody or been following somebody or avoiding somebody, or may
have gone to see a spectacle. Thus to say that chance is a thing contrary
to rule is correct. For 'rule' applies to what is always true or true for
the most part, whereas chance belongs to a third type of event. Hence,
to conclude, since causes of this kind are indefinite, chance too is indefinite.
(Yet in some cases one might raise the question whether any incidental
fact might be the cause of the chance occurrence, e.g. of health the fresh
air or the sun's heat may be the cause, but having had one's hair cut cannot;
for some incidental causes are more relevant to the effect than
others.)

Chance or fortune is called 'good' when the result is good, 'evil'
when it is evil. The terms 'good fortune' and 'ill fortune' are used when
either result is of considerable magnitude. Thus one who comes within an
ace of some great evil or great good is said to be fortunate or unfortunate.
The mind affirms the essence of the attribute, ignoring the hair's breadth
of difference. Further, it is with reason that good fortune is regarded
as unstable; for chance is unstable, as none of the things which result
from it can be invariable or normal.

Both are then, as I have said, incidental causes-both chance and
spontaneity-in the sphere of things which are capable of coming to pass
not necessarily, nor normally, and with reference to such of these as might
come to pass for the sake of something.

Part 6

They differ in that 'spontaneity' is the wider term. Every result
of chance is from what is spontaneous, but not everything that is from
what is spontaneous is from chance.

Chance and what results from chance are appropriate to agents that
are capable of good fortune and of moral action generally. Therefore necessarily
chance is in the sphere of moral actions. This is indicated by the fact
that good fortune is thought to be the same, or nearly the same, as happiness,
and happiness to be a kind of moral action, since it is well-doing. Hence
what is not capable of moral action cannot do anything by chance. Thus
an inanimate thing or a lower animal or a child cannot do anything by chance,
because it is incapable of deliberate intention; nor can 'good fortune'
or 'ill fortune' be ascribed to them, except metaphorically, as Protarchus,
for example, said that the stones of which altars are made are fortunate
because they are held in honour, while their fellows are trodden under
foot. Even these things, however, can in a way be affected by chance, when
one who is dealing with them does something to them by chance, but not
otherwise.

The spontaneous on the other hand is found both in the lower animals
and in many inanimate objects. We say, for example, that the horse came
'spontaneously', because, though his coming saved him, he did not come
for the sake of safety. Again, the tripod fell 'of itself', because, though
when it fell it stood on its feet so as to serve for a seat, it did not
fall for the sake of that.

Hence it is clear that events which (1) belong to the general class
of things that may come to pass for the sake of something, (2) do not come
to pass for the sake of what actually results, and (3) have an external
cause, may be described by the phrase 'from spontaneity'. These 'spontaneous'
events are said to be 'from chance' if they have the further characteristics
of being the objects of deliberate intention and due to agents capable
of that mode of action. This is indicated by the phrase 'in vain', which
is used when A which is for the sake of B, does not result in B. For instance,
taking a walk is for the sake of evacuation of the bowels; if this does
not follow after walking, we say that we have walked 'in vain' and that
the walking was 'vain'. This implies that what is naturally the means to
an end is 'in vain', when it does not effect the end towards which it was
the natural means-for it would be absurd for a man to say that he had bathed
in vain because the sun was not eclipsed, since the one was not done with
a view to the other. Thus the spontaneous is even according to its derivation
the case in which the thing itself happens in vain. The stone that struck
the man did not fall for the purpose of striking him; therefore it fell
spontaneously, because it might have fallen by the action of an agent and
for the purpose of striking. The difference between spontaneity and what
results by chance is greatest in things that come to be by nature; for
when anything comes to be contrary to nature, we do not say that it came
to be by chance, but by spontaneity. Yet strictly this too is different
from the spontaneous proper; for the cause of the latter is external, that
of the former internal.

We have now explained what chance is and what spontaneity is, and
in what they differ from each other. Both belong to the mode of causation
'source of change', for either some natural or some intelligent agent is
always the cause; but in this sort of causation the number of possible
causes is infinite.

Spontaneity and chance are causes of effects which though they
might result from intelligence or nature, have in fact been caused by something
incidentally. Now since nothing which is incidental is prior to what is
per se, it is clear that no incidental cause can be prior to a cause per
se. Spontaneity and chance, therefore, are posterior to intelligence and
nature. Hence, however true it may be that the heavens are due to spontaneity,
it will still be true that intelligence and nature will be prior causes
of this All and of many things in it besides.